[v2,2/6] bfd: Improve nm and objdump without section header

Message ID 20210703201402.1136267-3-hjl.tools@gmail.com
State New
Headers show
Series
  • ELF: Strip section header in ELF objects
Related show

Commit Message

H.J. Lu via Binutils July 3, 2021, 8:13 p.m.
When there is no section header in an executable or shared library, we
reconstruct dynamic symbol table from the PT_DYNAMIC segment, which
contains DT_HASH/DT_GNU_HASH/DT_MIPS_XHASH, DT_STRTAB, DT_SYMTAB,
DT_STRSZ, and DT_SYMENT entries, to improve nm and objdump.  For DT_HASH,
the number of dynamic symbol table entries equals the number of chains.
For DT_GNU_HASH/DT_MIPS_XHASH, only defined symbols with non-STB_LOCAL
indings are in hash table.  Since DT_GNU_HASH/DT_MIPS_XHASH place all
symbols with STB_LOCAL binding before symbols with other bindings and
all undefined symbols defined ones in dynamic symbol table, the highest
symbol index in DT_GNU_HASH/DT_MIPS_XHASH is the highest dynamic symbol
table index.  We can also get symbol version from DT_VERSYM, DT_VERDEF
and DT_VERNEED entries.

dt_symtab, dt_versym, dt_verdef, dt_verneed, dt_symtab_count,
dt_verdef_count, dt_verneed_count and dt_strtab are added to
elf_obj_tdata to store dynamic symbol table information.

	PR ld/25617
	* elf-bfd.h (elf_obj_tdata): Add dt_symtab, dt_verdef, dt_verneed,
	dt_symtab_count, dt_verdef_count, dt_verneed_count and dt_strtab.
	(elf_use_dt_symtab_p): New.
	(_bfd_elf_get_dynamic_symbols): Likewise.
	(_bfd_elf_get_section_from_dynamic_symbol): Likewise.
	* elf.c (bfd_elf_get_elf_syms): Use dynamic symbol table if
	neeeded.
	(_bfd_elf_get_dynamic_symtab_upper_bound): Likewise.
	(_bfd_elf_slurp_version_tables): Likewise.
	(offset_from_vma): New function.
	(get_hash_table_data): Likewise.
	(_bfd_elf_get_dynamic_symbols): Likewise.
	(_bfd_elf_get_section_from_dynamic_symbol): Likewise.
	(_bfd_elf_get_symbol_version_name): Likewise.
	* elfcode.h (elf_object_p): Call _bfd_elf_get_dynamic_symbols
	to reconstruct dynamic symbol table from PT_DYNAMIC segment if
	there is no section header.
	(elf_slurp_symbol_table): Use dynamic symbol table if neeeded.
	Don't free isymbuf when dynamic symbol table is used.
	* elflink.c (elf_link_is_defined_archive_symbol): Return wrong
	format error when dynamic symbol table is used.
	(elf_link_add_object_symbols): Likewise.
---
 bfd/elf-bfd.h |  15 +
 bfd/elf.c     | 740 ++++++++++++++++++++++++++++++++++++++++++++++----
 bfd/elfcode.h |  55 +++-
 bfd/elflink.c |  12 +
 4 files changed, 756 insertions(+), 66 deletions(-)

-- 
2.31.1

Patch

diff --git a/bfd/elf-bfd.h b/bfd/elf-bfd.h
index 101c2fdf50d..14fba3e5512 100644
--- a/bfd/elf-bfd.h
+++ b/bfd/elf-bfd.h
@@ -1941,6 +1941,14 @@  struct elf_obj_tdata
   Elf_Internal_Shdr dynversym_hdr;
   Elf_Internal_Shdr dynverref_hdr;
   Elf_Internal_Shdr dynverdef_hdr;
+  Elf_Internal_Sym *dt_symtab;
+  bfd_byte *dt_versym;
+  bfd_byte *dt_verdef;
+  bfd_byte *dt_verneed;
+  size_t dt_symtab_count;
+  size_t dt_verdef_count;
+  size_t dt_verneed_count;
+  char *dt_strtab;
   elf_section_list * symtab_shndx_list;
   bfd_vma gp;				/* The gp value */
   unsigned int gp_size;			/* The gp size */
@@ -2097,6 +2105,7 @@  struct elf_obj_tdata
 #define elf_dyn_lib_class(bfd)	(elf_tdata(bfd) -> dyn_lib_class)
 #define elf_bad_symtab(bfd)	(elf_tdata(bfd) -> bad_symtab)
 #define elf_flags_init(bfd)	(elf_tdata(bfd) -> o->flags_init)
+#define elf_use_dt_symtab_p(bfd) (elf_tdata(bfd) -> dt_symtab_count != 0)
 #define elf_known_obj_attributes(bfd) (elf_tdata (bfd) -> known_obj_attributes)
 #define elf_other_obj_attributes(bfd) (elf_tdata (bfd) -> other_obj_attributes)
 #define elf_known_obj_attributes_proc(bfd) \
@@ -2470,6 +2479,12 @@  extern bfd_reloc_status_type bfd_elf_perform_complex_relocation
 extern bool _bfd_elf_setup_sections
   (bfd *);
 
+extern bool _bfd_elf_get_dynamic_symbols
+  (bfd *, Elf_Internal_Phdr *, Elf_Internal_Phdr *, size_t,
+   bfd_size_type);
+extern asection *_bfd_elf_get_section_from_dynamic_symbol
+  (bfd *, Elf_Internal_Sym *);
+
 extern struct bfd_link_hash_entry *bfd_elf_define_start_stop
   (struct bfd_link_info *, const char *, asection *);
 
diff --git a/bfd/elf.c b/bfd/elf.c
index 697d1ee7282..63e51c2dd01 100644
--- a/bfd/elf.c
+++ b/bfd/elf.c
@@ -406,6 +406,17 @@  bfd_elf_get_elf_syms (bfd *ibfd,
   if (symcount == 0)
     return intsym_buf;
 
+  if (elf_use_dt_symtab_p (ibfd))
+    {
+      /* Use dynamic symbol table.  */
+      if (elf_tdata (ibfd)->dt_symtab_count != (symcount + symoffset))
+	{
+	  bfd_set_error (bfd_error_invalid_operation);
+	  return NULL;
+	}
+      return elf_tdata (ibfd)->dt_symtab + symoffset;
+    }
+
   /* Normal syms might have section extension entries.  */
   shndx_hdr = NULL;
   if (elf_symtab_shndx_list (ibfd) != NULL)
@@ -1895,6 +1906,560 @@  _bfd_elf_print_private_bfd_data (bfd *abfd, void *farg)
   return false;
 }
 
+/* Find the file offset corresponding to VMA by using the program
+   headers.  */
+
+static file_ptr
+offset_from_vma (Elf_Internal_Phdr *phdrs, size_t phnum, bfd_vma vma,
+		 size_t size, size_t *max_size_p)
+{
+  Elf_Internal_Phdr *seg;
+  size_t i;
+
+  for (seg = phdrs, i = 0; i < phnum; ++seg, ++i)
+    if (seg->p_type == PT_LOAD
+	&& vma >= (seg->p_vaddr & -seg->p_align)
+	&& vma + size <= seg->p_vaddr + seg->p_filesz)
+      {
+	if (max_size_p)
+	  *max_size_p = seg->p_vaddr + seg->p_filesz - vma;
+	return (file_ptr) (vma - seg->p_vaddr + seg->p_offset);
+      }
+
+  bfd_set_error (bfd_error_invalid_operation);
+  return (file_ptr) -1;
+}
+
+/* Convert hash table to internal form.  */
+
+static bfd_vma *
+get_hash_table_data (bfd *abfd, bfd_size_type number,
+		     unsigned int ent_size, bfd_size_type filesize)
+{
+  unsigned char *e_data = NULL;
+  bfd_vma *i_data = NULL;
+  bfd_size_type size;
+
+  if (ent_size != 4 && ent_size != 8)
+    return NULL;
+
+  /* If the size_t type is smaller than the bfd_size_type, eg because
+     you are building a 32-bit tool on a 64-bit host, then make sure
+     that when (number) is cast to (size_t) no information is lost.  */
+  if (sizeof (size_t) < sizeof (bfd_size_type)
+      && (bfd_size_type) ((size_t) number) != number)
+    {
+      bfd_set_error (bfd_error_file_too_big);
+      return NULL;
+    }
+
+  size = ent_size * number;
+  /* Be kind to memory checkers (eg valgrind, address sanitizer) by not
+     attempting to allocate memory when the read is bound to fail.  */
+  if (size > filesize
+      || number >= ~(size_t) 0 / ent_size
+      || number >= ~(size_t) 0 / sizeof (*i_data))
+    {
+      bfd_set_error (bfd_error_file_too_big);
+      return NULL;
+    }
+
+  e_data = _bfd_malloc_and_read (abfd, size, size);
+  if (e_data == NULL)
+    return NULL;
+
+  i_data = (bfd_vma *) bfd_malloc (number * sizeof (*i_data));
+  if (i_data == NULL)
+    {
+      free (e_data);
+      return NULL;
+    }
+
+  if (ent_size == 4)
+    while (number--)
+      i_data[number] = bfd_get_32 (abfd, e_data + number * ent_size);
+  else
+    while (number--)
+      i_data[number] = bfd_get_64 (abfd, e_data + number * ent_size);
+
+  free (e_data);
+  return i_data;
+}
+
+/* Address of .MIPS.xhash section.  FIXME: What is the best way to
+   support DT_MIPS_XHASH?  */
+#define DT_MIPS_XHASH	       0x70000036
+
+/* Reconstruct dynamic symbol table from PT_DYNAMIC segment.  */
+
+bool
+_bfd_elf_get_dynamic_symbols (bfd *abfd, Elf_Internal_Phdr *phdr,
+			      Elf_Internal_Phdr *phdrs, size_t phnum,
+			      bfd_size_type filesize)
+{
+  bfd_byte *extdyn, *extdynend;
+  size_t extdynsize;
+  void (*swap_dyn_in) (bfd *, const void *, Elf_Internal_Dyn *);
+  bool (*swap_symbol_in) (bfd *, const void *, const void *,
+			  Elf_Internal_Sym *);
+  Elf_Internal_Dyn dyn;
+  bfd_vma dt_hash = 0;
+  bfd_vma dt_gnu_hash = 0;
+  bfd_vma dt_mips_xhash = 0;
+  bfd_vma dt_strtab = 0;
+  bfd_vma dt_symtab = 0;
+  size_t dt_strsz = 0;
+  bfd_vma dt_versym = 0;
+  bfd_vma dt_verdef = 0;
+  bfd_vma dt_verneed = 0;
+  bfd_byte *dynbuf = NULL;
+  char *strbuf = NULL;
+  bfd_vma *gnubuckets = NULL;
+  bfd_vma *gnuchains = NULL;
+  bfd_vma *mipsxlat = NULL;
+  file_ptr saved_filepos, filepos;
+  bool res = false;
+  size_t amt;
+  bfd_byte *esymbuf = NULL, *esym;
+  bfd_size_type symcount;
+  Elf_Internal_Sym *isymbuf = NULL;
+  Elf_Internal_Sym *isym, *isymend;
+  bfd_byte *versym = NULL;
+  bfd_byte *verdef = NULL;
+  bfd_byte *verneed = NULL;
+  size_t verdef_size;
+  size_t verneed_size;
+  size_t extsym_size;
+  const struct elf_backend_data *bed;
+
+  /* Return TRUE if symbol table is bad.  */
+  if (elf_bad_symtab (abfd))
+    return true;
+
+  /* Return TRUE if DT_HASH/DT_GNU_HASH have bee processed before.  */
+  if (elf_tdata (abfd)->dt_strtab != NULL)
+    return true;
+
+  bed = get_elf_backend_data (abfd);
+
+  /* Save file position for elf_object_p.  */
+  saved_filepos = bfd_tell (abfd);
+
+  if (bfd_seek (abfd, phdr->p_offset, SEEK_SET) != 0)
+    goto error_return;
+
+  dynbuf = _bfd_malloc_and_read (abfd, phdr->p_filesz, phdr->p_filesz);
+  if (dynbuf == NULL)
+    goto error_return;
+
+  extsym_size = bed->s->sizeof_sym;
+  extdynsize = bed->s->sizeof_dyn;
+  swap_dyn_in = bed->s->swap_dyn_in;
+
+  extdyn = dynbuf;
+  if (phdr->p_filesz < extdynsize)
+    goto error_return;
+  extdynend = extdyn + phdr->p_filesz;
+  for (; extdyn <= (extdynend - extdynsize); extdyn += extdynsize)
+    {
+      swap_dyn_in (abfd, extdyn, &dyn);
+
+      if (dyn.d_tag == DT_NULL)
+	break;
+
+      switch (dyn.d_tag)
+	{
+	case DT_HASH:
+	  dt_hash = dyn.d_un.d_val;
+	  break;
+	case DT_GNU_HASH:
+	  if (bed->elf_machine_code != EM_MIPS
+	      && bed->elf_machine_code != EM_MIPS_RS3_LE)
+	    dt_gnu_hash = dyn.d_un.d_val;
+	  break;
+	case DT_STRTAB:
+	  dt_strtab = dyn.d_un.d_val;
+	  break;
+	case DT_SYMTAB:
+	  dt_symtab = dyn.d_un.d_val;
+	  break;
+	case DT_STRSZ:
+	  dt_strsz = dyn.d_un.d_val;
+	  break;
+	case DT_SYMENT:
+	  if (dyn.d_un.d_val != extsym_size)
+	    goto error_return;
+	  break;
+	case DT_VERSYM:
+	  dt_versym = dyn.d_un.d_val;
+	  break;
+	case DT_VERDEF:
+	  dt_verdef = dyn.d_un.d_val;
+	  break;
+	case DT_VERNEED:
+	  dt_verneed = dyn.d_un.d_val;
+	  break;
+	default:
+	  if (dyn.d_tag == DT_MIPS_XHASH
+	      && (bed->elf_machine_code == EM_MIPS
+		  || bed->elf_machine_code == EM_MIPS_RS3_LE))
+	    {
+	      dt_gnu_hash = dyn.d_un.d_val;
+	      dt_mips_xhash = dyn.d_un.d_val;
+	    }
+	  break;
+	}
+    }
+
+  /* Check if we can reconstruct dynamic symbol table from PT_DYNAMIC
+     segment.  */
+  if ((!dt_hash && !dt_gnu_hash)
+      || !dt_strtab
+      || !dt_symtab
+      || !dt_strsz)
+    goto error_return;
+
+  /* Get dynamic string table.  */
+  filepos = offset_from_vma (phdrs, phnum, dt_strtab, dt_strsz, NULL);
+  if (filepos == (file_ptr) -1
+      || bfd_seek (abfd, filepos, SEEK_SET) != 0)
+    goto error_return;
+
+  /* Dynamic string table must be valid until ABFD is closed.  */
+  strbuf = (char *) _bfd_alloc_and_read (abfd, dt_strsz, dt_strsz);
+  if (strbuf == NULL)
+    goto error_return;
+
+  /* Get the real symbol count from DT_HASH or DT_GNU_HASH.  Prefer
+     DT_HASH since it is simpler than DT_GNU_HASH.  */
+  if (dt_hash)
+    {
+      unsigned char nb[16];
+      unsigned int hash_ent_size;
+
+      switch (bed->elf_machine_code)
+	{
+	case EM_ALPHA:
+	case EM_S390:
+	case EM_S390_OLD:
+	  if (bed->s->elfclass == ELFCLASS64)
+	    {
+	      hash_ent_size = 8;
+	      break;
+	    }
+	  /* FALLTHROUGH */
+	default:
+	  hash_ent_size = 4;
+	  break;
+	}
+
+      filepos = offset_from_vma (phdrs, phnum, dt_hash, sizeof (nb),
+				 NULL);
+      if (filepos == (file_ptr) -1
+	  || bfd_seek (abfd, filepos, SEEK_SET) != 0
+	  || (bfd_bread (nb, 2 * hash_ent_size, abfd)
+	      != (2 * hash_ent_size)))
+	goto error_return;
+
+      /* The number of dynamic symbol table entries equals the number
+	 of chains.  */
+      if (hash_ent_size == 8)
+	symcount = bfd_get_64 (abfd, nb + hash_ent_size);
+      else
+	symcount = bfd_get_32 (abfd, nb + hash_ent_size);
+    }
+  else
+    {
+      /* For DT_GNU_HASH, only defined symbols with non-STB_LOCAL
+	 bindings are in hash table.  Since in dynamic symbol table,
+	 all symbols with STB_LOCAL binding are placed before symbols
+	 with other bindings and all undefined symbols are placed
+	 before defined ones, the highest symbol index in DT_GNU_HASH
+	 is the highest dynamic symbol table index.  */
+      unsigned char nb[16];
+      bfd_vma ngnubuckets;
+      bfd_vma gnusymidx;
+      size_t i, ngnuchains;
+      bfd_vma maxchain = 0xffffffff, bitmaskwords;
+      bfd_vma buckets_vma;
+
+      filepos = offset_from_vma (phdrs, phnum, dt_gnu_hash,
+				 sizeof (nb), NULL);
+      if (filepos == (file_ptr) -1
+	  || bfd_seek (abfd, filepos, SEEK_SET) != 0
+	  || bfd_bread (nb, sizeof (nb), abfd) != sizeof (nb))
+	goto error_return;
+
+      ngnubuckets = bfd_get_32 (abfd, nb);
+      gnusymidx = bfd_get_32 (abfd, nb + 4);
+      bitmaskwords = bfd_get_32 (abfd, nb + 8);
+      buckets_vma = dt_gnu_hash + 16;
+      if (bed->s->elfclass == ELFCLASS32)
+	buckets_vma += bitmaskwords * 4;
+      else
+	buckets_vma += bitmaskwords * 8;
+      filepos = offset_from_vma (phdrs, phnum, buckets_vma, 4, NULL);
+      if (filepos == (file_ptr) -1
+	  || bfd_seek (abfd, filepos, SEEK_SET) != 0)
+	goto error_return;
+
+      gnubuckets = get_hash_table_data (abfd, ngnubuckets, 4, filesize);
+      if (gnubuckets == NULL)
+	goto error_return;
+
+      for (i = 0; i < ngnubuckets; i++)
+	if (gnubuckets[i] != 0)
+	  {
+	    if (gnubuckets[i] < gnusymidx)
+	      goto error_return;
+
+	    if (maxchain == 0xffffffff || gnubuckets[i] > maxchain)
+	      maxchain = gnubuckets[i];
+	  }
+
+      if (maxchain == 0xffffffff)
+	goto error_return;
+
+      maxchain -= gnusymidx;
+      filepos = offset_from_vma (phdrs, phnum,
+				 (buckets_vma +
+				  4 * (ngnubuckets + maxchain)),
+				 4, NULL);
+      if (filepos == (file_ptr) -1
+	  || bfd_seek (abfd, filepos, SEEK_SET) != 0)
+	goto error_return;
+
+      do
+	{
+	  if (bfd_bread (nb, 4, abfd) != 4)
+	    goto error_return;
+	  ++maxchain;
+	  if (maxchain == 0)
+	    goto error_return;
+	}
+      while ((bfd_get_32 (abfd, nb) & 1) == 0);
+
+      filepos = offset_from_vma (phdrs, phnum,
+				 (buckets_vma + 4 * ngnubuckets),
+				 4, NULL);
+      if (filepos == (file_ptr) -1
+	  || bfd_seek (abfd, filepos, SEEK_SET) != 0)
+	goto error_return;
+
+      gnuchains = get_hash_table_data (abfd, maxchain, 4, filesize);
+      if (gnubuckets == NULL)
+	goto error_return;
+      ngnuchains = maxchain;
+
+      if (dt_mips_xhash)
+	{
+	  filepos = offset_from_vma (phdrs, phnum,
+				     (buckets_vma
+				      + 4 * (ngnubuckets + maxchain)),
+				     4, NULL);
+	  if (filepos == (file_ptr) -1
+	      || bfd_seek (abfd, filepos, SEEK_SET) != 0)
+	    goto error_return;
+
+	  mipsxlat = get_hash_table_data (abfd, maxchain, 4, filesize);
+	  if (mipsxlat == NULL)
+	    goto error_return;
+	}
+
+      symcount = 0;
+      for (i = 0; i < ngnubuckets; ++i)
+	if (gnubuckets[i] != 0)
+	  {
+	    bfd_vma si = gnubuckets[i];
+	    bfd_vma off = si - gnusymidx;
+	    do
+	      {
+		if (mipsxlat)
+		  {
+		    if (mipsxlat[off] >= symcount)
+		      symcount = mipsxlat[off] + 1;
+		  }
+		else
+		  {
+		    if (si >= symcount)
+		      symcount = si + 1;
+		  }
+		si++;
+	      }
+	    while (off < ngnuchains && (gnuchains[off++] & 1) == 0);
+	  }
+    }
+
+  /* Swap in dynamic symbol table.  */
+  if (_bfd_mul_overflow (symcount, extsym_size, &amt))
+    {
+      bfd_set_error (bfd_error_file_too_big);
+      goto error_return;
+    }
+
+  filepos = offset_from_vma (phdrs, phnum, dt_symtab, amt, NULL);
+  if (filepos == (file_ptr) -1
+      || bfd_seek (abfd, filepos, SEEK_SET) != 0)
+    goto error_return;
+  esymbuf = _bfd_malloc_and_read (abfd, amt, amt);
+  if (esymbuf == NULL)
+    goto error_return;
+
+  if (_bfd_mul_overflow (symcount, sizeof (Elf_Internal_Sym), &amt))
+    {
+      bfd_set_error (bfd_error_file_too_big);
+      goto error_return;
+    }
+
+  /* Dynamic symbol table must be valid until ABFD is closed.  */
+  isymbuf = (Elf_Internal_Sym *) bfd_alloc (abfd, amt);
+  if (isymbuf == NULL)
+    goto error_return;
+
+  swap_symbol_in = bed->s->swap_symbol_in;
+
+  /* Convert the symbols to internal form.  */
+  isymend = isymbuf + symcount;
+  for (esym = esymbuf, isym = isymbuf;
+       isym < isymend;
+       esym += extsym_size, isym++)
+    if (!swap_symbol_in (abfd, esym, NULL, isym)
+	|| isym->st_name >= dt_strsz)
+      {
+	bfd_set_error (bfd_error_invalid_operation);
+	goto error_return;
+      }
+
+  if (dt_versym)
+    {
+      /* Swap in DT_VERSYM.  */
+      if (_bfd_mul_overflow (symcount, 2, &amt))
+	{
+	  bfd_set_error (bfd_error_file_too_big);
+	  goto error_return;
+	}
+
+      filepos = offset_from_vma (phdrs, phnum, dt_versym, amt, NULL);
+      if (filepos == (file_ptr) -1
+	  || bfd_seek (abfd, filepos, SEEK_SET) != 0)
+	goto error_return;
+
+      /* DT_VERSYM info must be valid until ABFD is closed.  */
+      versym = _bfd_alloc_and_read (abfd, amt, amt);
+
+      if (dt_verdef)
+	{
+	  /* Read in DT_VERDEF.  */
+	  filepos = offset_from_vma (phdrs, phnum, dt_verdef,
+				     0, &verdef_size);
+	  if (filepos == (file_ptr) -1
+	      || bfd_seek (abfd, filepos, SEEK_SET) != 0)
+	    goto error_return;
+
+	  /* DT_VERDEF info must be valid until ABFD is closed.  */
+	  verdef = _bfd_alloc_and_read (abfd, verdef_size,
+					verdef_size);
+	}
+
+      if (dt_verneed)
+	{
+	  /* Read in DT_VERNEED.  */
+	  filepos = offset_from_vma (phdrs, phnum, dt_verneed,
+				     0, &verneed_size);
+	  if (filepos == (file_ptr) -1
+	      || bfd_seek (abfd, filepos, SEEK_SET) != 0)
+	    goto error_return;
+
+	  /* DT_VERNEED info must be valid until ABFD is closed.  */
+	  verneed = _bfd_alloc_and_read (abfd, verneed_size,
+					 verneed_size);
+	}
+    }
+
+  elf_tdata (abfd)->dt_strtab = strbuf;
+  elf_tdata (abfd)->dt_symtab = isymbuf;
+  elf_tdata (abfd)->dt_symtab_count = symcount;
+  elf_tdata (abfd)->dt_versym = versym;
+  elf_tdata (abfd)->dt_verdef = verdef;
+  elf_tdata (abfd)->dt_verneed = verneed;
+  elf_tdata (abfd)->dt_verdef_count
+    = verdef_size / sizeof (Elf_External_Verdef);
+  elf_tdata (abfd)->dt_verneed_count
+    = verneed_size / sizeof (Elf_External_Verneed);
+
+  res = true;
+
+ error_return:
+  /* Restore file position for elf_object_p.  */
+  if (bfd_seek (abfd, saved_filepos, SEEK_SET) != 0)
+    res = false;
+  if (dynbuf != NULL)
+    free (dynbuf);
+  if (esymbuf != NULL)
+    free (esymbuf);
+  if (gnubuckets != NULL)
+    free (gnubuckets);
+  if (gnuchains != NULL)
+    free (gnuchains);
+  if (mipsxlat != NULL)
+    free (mipsxlat);
+  return res;
+}
+
+/* Reconstruct section from dynamic symbol.  */
+
+asection *
+_bfd_elf_get_section_from_dynamic_symbol (bfd *abfd,
+					  Elf_Internal_Sym *isym)
+{
+  asection *sec;
+  flagword flags;
+
+  if (!elf_use_dt_symtab_p (abfd))
+    return NULL;
+
+  flags = SEC_ALLOC | SEC_LOAD;
+  switch (ELF_ST_TYPE (isym->st_info))
+    {
+    case STT_FUNC:
+    case STT_GNU_IFUNC:
+      sec = bfd_get_section_by_name (abfd, ".text");
+      if (sec == NULL)
+	sec = bfd_make_section_with_flags (abfd,
+					   ".text",
+					   flags | SEC_CODE);
+      break;
+    case STT_COMMON:
+      sec = bfd_com_section_ptr;
+      break;
+    case STT_OBJECT:
+      sec = bfd_get_section_by_name (abfd, ".data");
+      if (sec == NULL)
+	sec = bfd_make_section_with_flags (abfd,
+					   ".data",
+					   flags | SEC_DATA);
+      break;
+    case STT_TLS:
+      sec = bfd_get_section_by_name (abfd, ".tdata");
+      if (sec == NULL)
+	sec = bfd_make_section_with_flags (abfd,
+					   ".tdata",
+					   (flags
+					    | SEC_DATA
+					    | SEC_THREAD_LOCAL));
+      break;
+    default:
+      sec = bfd_abs_section_ptr;
+      break;
+    }
+
+  /* NB: Don't place this section in output.  */
+  if (sec && 0)
+    sec->output_section = bfd_abs_section_ptr;
+
+  return sec;
+}
+
 /* Get version name.  If BASE_P is TRUE, return "Base" for VER_FLG_BASE
    and return symbol version for symbol version itself.   */
 
@@ -1904,8 +2469,11 @@  _bfd_elf_get_symbol_version_string (bfd *abfd, asymbol *symbol,
 				    bool *hidden)
 {
   const char *version_string = NULL;
-  if (elf_dynversym (abfd) != 0
-      && (elf_dynverdef (abfd) != 0 || elf_dynverref (abfd) != 0))
+  if ((elf_dynversym (abfd) != 0
+       && (elf_dynverdef (abfd) != 0 || elf_dynverref (abfd) != 0))
+      || (elf_tdata (abfd)->dt_versym != NULL
+	  && (elf_tdata (abfd)->dt_verdef != NULL
+	      || elf_tdata (abfd)->dt_verneed != NULL)))
     {
       unsigned int vernum = ((elf_symbol_type *) symbol)->version;
 
@@ -8500,6 +9068,11 @@  _bfd_elf_get_dynamic_symtab_upper_bound (bfd *abfd)
 
   if (elf_dynsymtab (abfd) == 0)
     {
+      /* Check if there is dynamic symbol table.  */
+      symcount = elf_tdata (abfd)->dt_symtab_count;
+      if (symcount)
+	goto compute_symtab_size;
+
       bfd_set_error (bfd_error_invalid_operation);
       return -1;
     }
@@ -8510,6 +9083,8 @@  _bfd_elf_get_dynamic_symtab_upper_bound (bfd *abfd)
       bfd_set_error (bfd_error_file_too_big);
       return -1;
     }
+
+ compute_symtab_size:
   symtab_size = symcount * (sizeof (asymbol *));
   if (symcount == 0)
     symtab_size = sizeof (asymbol *);
@@ -8710,36 +9285,51 @@  _bfd_elf_slurp_version_tables (bfd *abfd, bool default_imported_symver)
   unsigned int freeidx = 0;
   size_t amt;
 
-  if (elf_dynverref (abfd) != 0)
+  if (elf_dynverref (abfd) != 0 || elf_tdata (abfd)->dt_verneed != NULL)
     {
       Elf_Internal_Shdr *hdr;
       Elf_External_Verneed *everneed;
       Elf_Internal_Verneed *iverneed;
       unsigned int i;
       bfd_byte *contents_end;
+      size_t verneed_count;
+      size_t verneed_size;
 
-      hdr = &elf_tdata (abfd)->dynverref_hdr;
-
-      if (hdr->sh_info == 0
-	  || hdr->sh_info > hdr->sh_size / sizeof (Elf_External_Verneed))
+      if (elf_tdata (abfd)->dt_verneed != NULL)
 	{
-	error_return_bad_verref:
-	  _bfd_error_handler
-	    (_("%pB: .gnu.version_r invalid entry"), abfd);
-	  bfd_set_error (bfd_error_bad_value);
-	error_return_verref:
-	  elf_tdata (abfd)->verref = NULL;
-	  elf_tdata (abfd)->cverrefs = 0;
-	  goto error_return;
+	  hdr = NULL;
+	  contents = elf_tdata (abfd)->dt_verneed;
+	  verneed_count = elf_tdata (abfd)->dt_verneed_count;
+	  verneed_size = verneed_count * sizeof (Elf_External_Verneed);
 	}
+      else
+	{
+	  hdr = &elf_tdata (abfd)->dynverref_hdr;
+	  if (hdr->sh_info == 0
+	      || hdr->sh_info > hdr->sh_size / sizeof (Elf_External_Verneed))
+	    {
+	    error_return_bad_verref:
+	      _bfd_error_handler
+		(_("%pB: .gnu.version_r invalid entry"), abfd);
+	      bfd_set_error (bfd_error_bad_value);
+	    error_return_verref:
+	      elf_tdata (abfd)->verref = NULL;
+	      elf_tdata (abfd)->cverrefs = 0;
+	      goto error_return;
+	    }
 
-      if (bfd_seek (abfd, hdr->sh_offset, SEEK_SET) != 0)
-	goto error_return_verref;
-      contents = _bfd_malloc_and_read (abfd, hdr->sh_size, hdr->sh_size);
-      if (contents == NULL)
-	goto error_return_verref;
+	  if (bfd_seek (abfd, hdr->sh_offset, SEEK_SET) != 0)
+	    goto error_return_verref;
+	  contents = _bfd_malloc_and_read (abfd, hdr->sh_size, hdr->sh_size);
+	  if (contents == NULL)
+	    goto error_return_verref;
+
+	  verneed_size = hdr->sh_size;
+	  verneed_count = hdr->sh_info;
+	}
 
-      if (_bfd_mul_overflow (hdr->sh_info, sizeof (Elf_Internal_Verneed), &amt))
+      if (_bfd_mul_overflow (verneed_count,
+			     sizeof (Elf_Internal_Verneed), &amt))
 	{
 	  bfd_set_error (bfd_error_file_too_big);
 	  goto error_return_verref;
@@ -8750,10 +9340,11 @@  _bfd_elf_slurp_version_tables (bfd *abfd, bool default_imported_symver)
 
       BFD_ASSERT (sizeof (Elf_External_Verneed)
 		  == sizeof (Elf_External_Vernaux));
-      contents_end = contents + hdr->sh_size - sizeof (Elf_External_Verneed);
+      contents_end = (contents + verneed_size
+		      - sizeof (Elf_External_Verneed));
       everneed = (Elf_External_Verneed *) contents;
       iverneed = elf_tdata (abfd)->verref;
-      for (i = 0; i < hdr->sh_info; i++, iverneed++)
+      for (i = 0; i < verneed_count; i++, iverneed++)
 	{
 	  Elf_External_Vernaux *evernaux;
 	  Elf_Internal_Vernaux *ivernaux;
@@ -8763,9 +9354,13 @@  _bfd_elf_slurp_version_tables (bfd *abfd, bool default_imported_symver)
 
 	  iverneed->vn_bfd = abfd;
 
-	  iverneed->vn_filename =
-	    bfd_elf_string_from_elf_section (abfd, hdr->sh_link,
-					     iverneed->vn_file);
+	  if (elf_use_dt_symtab_p (abfd))
+	    iverneed->vn_filename
+	      = elf_tdata (abfd)->dt_strtab + iverneed->vn_file;
+	  else
+	    iverneed->vn_filename
+	      = bfd_elf_string_from_elf_section (abfd, hdr->sh_link,
+						 iverneed->vn_file);
 	  if (iverneed->vn_filename == NULL)
 	    goto error_return_bad_verref;
 
@@ -8796,9 +9391,13 @@  _bfd_elf_slurp_version_tables (bfd *abfd, bool default_imported_symver)
 	    {
 	      _bfd_elf_swap_vernaux_in (abfd, evernaux, ivernaux);
 
-	      ivernaux->vna_nodename =
-		bfd_elf_string_from_elf_section (abfd, hdr->sh_link,
-						 ivernaux->vna_name);
+	      if (elf_use_dt_symtab_p (abfd))
+		ivernaux->vna_nodename
+		  = elf_tdata (abfd)->dt_strtab + ivernaux->vna_name;
+	      else
+		ivernaux->vna_nodename
+		  = bfd_elf_string_from_elf_section (abfd, hdr->sh_link,
+						     ivernaux->vna_name);
 	      if (ivernaux->vna_nodename == NULL)
 		goto error_return_bad_verref;
 
@@ -8837,11 +9436,12 @@  _bfd_elf_slurp_version_tables (bfd *abfd, bool default_imported_symver)
 	}
       elf_tdata (abfd)->cverrefs = i;
 
-      free (contents);
+      if (elf_tdata (abfd)->dt_verneed == NULL)
+	free (contents);
       contents = NULL;
     }
 
-  if (elf_dynverdef (abfd) != 0)
+  if (elf_dynverdef (abfd) != 0 || elf_tdata (abfd)->dt_verdef != NULL)
     {
       Elf_Internal_Shdr *hdr;
       Elf_External_Verdef *everdef;
@@ -8851,40 +9451,57 @@  _bfd_elf_slurp_version_tables (bfd *abfd, bool default_imported_symver)
       unsigned int i;
       unsigned int maxidx;
       bfd_byte *contents_end_def, *contents_end_aux;
+      size_t verdef_count;
+      size_t verdef_size;
 
-      hdr = &elf_tdata (abfd)->dynverdef_hdr;
-
-      if (hdr->sh_info == 0 || hdr->sh_size < sizeof (Elf_External_Verdef))
+      if (elf_tdata (abfd)->dt_verdef != NULL)
 	{
-	error_return_bad_verdef:
-	  _bfd_error_handler
-	    (_("%pB: .gnu.version_d invalid entry"), abfd);
-	  bfd_set_error (bfd_error_bad_value);
-	error_return_verdef:
-	  elf_tdata (abfd)->verdef = NULL;
-	  elf_tdata (abfd)->cverdefs = 0;
-	  goto error_return;
+	  hdr = NULL;
+	  contents = elf_tdata (abfd)->dt_verdef;
+	  verdef_count = elf_tdata (abfd)->dt_verdef_count;
+	  verdef_size = verdef_count * sizeof (Elf_External_Verdef);
 	}
+      else
+	{
+	  hdr = &elf_tdata (abfd)->dynverdef_hdr;
 
-      if (bfd_seek (abfd, hdr->sh_offset, SEEK_SET) != 0)
-	goto error_return_verdef;
-      contents = _bfd_malloc_and_read (abfd, hdr->sh_size, hdr->sh_size);
-      if (contents == NULL)
-	goto error_return_verdef;
+	  if (hdr->sh_info == 0
+	      || hdr->sh_size < sizeof (Elf_External_Verdef))
+	    {
+	    error_return_bad_verdef:
+	      _bfd_error_handler
+		(_("%pB: .gnu.version_d invalid entry"), abfd);
+	      bfd_set_error (bfd_error_bad_value);
+	    error_return_verdef:
+	      elf_tdata (abfd)->verdef = NULL;
+	      elf_tdata (abfd)->cverdefs = 0;
+	      goto error_return;
+	    }
+
+	  if (bfd_seek (abfd, hdr->sh_offset, SEEK_SET) != 0)
+	    goto error_return_verdef;
+	  contents = _bfd_malloc_and_read (abfd, hdr->sh_size, hdr->sh_size);
+	  if (contents == NULL)
+	    goto error_return_verdef;
 
-      BFD_ASSERT (sizeof (Elf_External_Verdef)
-		  >= sizeof (Elf_External_Verdaux));
-      contents_end_def = contents + hdr->sh_size
-			 - sizeof (Elf_External_Verdef);
-      contents_end_aux = contents + hdr->sh_size
-			 - sizeof (Elf_External_Verdaux);
+	  BFD_ASSERT (sizeof (Elf_External_Verdef)
+		      >= sizeof (Elf_External_Verdaux));
+
+	  verdef_count = hdr->sh_info;
+	  verdef_size = hdr->sh_size;
+	}
+
+      contents_end_def = (contents + verdef_size
+			  - sizeof (Elf_External_Verdef));
+      contents_end_aux = (contents + verdef_size
+			  - sizeof (Elf_External_Verdaux));
 
       /* We know the number of entries in the section but not the maximum
 	 index.  Therefore we have to run through all entries and find
 	 the maximum.  */
       everdef = (Elf_External_Verdef *) contents;
       maxidx = 0;
-      for (i = 0; i < hdr->sh_info; ++i)
+      for (i = 0; i < verdef_count; ++i)
 	{
 	  _bfd_elf_swap_verdef_in (abfd, everdef, &iverdefmem);
 
@@ -8924,7 +9541,7 @@  _bfd_elf_slurp_version_tables (bfd *abfd, bool default_imported_symver)
 
       everdef = (Elf_External_Verdef *) contents;
       iverdefarr = elf_tdata (abfd)->verdef;
-      for (i = 0; i < hdr->sh_info; i++)
+      for (i = 0; i < verdef_count; ++i)
 	{
 	  Elf_External_Verdaux *everdaux;
 	  Elf_Internal_Verdaux *iverdaux;
@@ -8967,9 +9584,13 @@  _bfd_elf_slurp_version_tables (bfd *abfd, bool default_imported_symver)
 	    {
 	      _bfd_elf_swap_verdaux_in (abfd, everdaux, iverdaux);
 
-	      iverdaux->vda_nodename =
-		bfd_elf_string_from_elf_section (abfd, hdr->sh_link,
-						 iverdaux->vda_name);
+	      if (elf_use_dt_symtab_p (abfd))
+		iverdaux->vda_nodename
+		  = elf_tdata (abfd)->dt_strtab + iverdaux->vda_name;
+	      else
+		iverdaux->vda_nodename
+		  = bfd_elf_string_from_elf_section (abfd, hdr->sh_link,
+						     iverdaux->vda_name);
 	      if (iverdaux->vda_nodename == NULL)
 		goto error_return_bad_verdef;
 
@@ -9004,7 +9625,8 @@  _bfd_elf_slurp_version_tables (bfd *abfd, bool default_imported_symver)
 		     ((bfd_byte *) everdef + iverdef->vd_next));
 	}
 
-      free (contents);
+      if (elf_tdata (abfd)->dt_verdef == NULL)
+	free (contents);
       contents = NULL;
     }
   else if (default_imported_symver)
diff --git a/bfd/elfcode.h b/bfd/elfcode.h
index 252f4cbd632..5653d7c1076 100644
--- a/bfd/elfcode.h
+++ b/bfd/elfcode.h
@@ -832,6 +832,21 @@  elf_object_p (bfd *abfd)
 	      _bfd_error_handler (_("warning: %pB has a program header "
 				    "with invalid alignment"), abfd);
 	    }
+	  if (i_phdr->p_filesz != 0)
+	    {
+	      if ((i_phdr->p_offset + i_phdr->p_filesz) > filesize)
+		goto got_no_match;
+	      /* Try to reconstruct dynamic symbol table from PT_DYNAMIC
+		 segment if there is no section header.  */
+	      if (i_phdr->p_type == PT_DYNAMIC
+		  && i_ehdrp->e_shstrndx == 0
+		  && i_ehdrp->e_shoff == 0
+		  && !_bfd_elf_get_dynamic_symbols (abfd, i_phdr,
+						    elf_tdata (abfd)->phdr,
+						    i_ehdrp->e_phnum,
+						    filesize))
+		goto got_no_match;
+	    }
 	}
     }
 
@@ -1224,7 +1239,9 @@  elf_slurp_symbol_table (bfd *abfd, asymbol **symptrs, bool dynamic)
       if ((elf_dynverdef (abfd) != 0
 	   && elf_tdata (abfd)->verdef == NULL)
 	  || (elf_dynverref (abfd) != 0
-	      && elf_tdata (abfd)->verref == NULL))
+	      && elf_tdata (abfd)->verref == NULL)
+	  || elf_tdata (abfd)->dt_verdef != NULL
+	  || elf_tdata (abfd)->dt_verneed != NULL)
 	{
 	  if (!_bfd_elf_slurp_version_tables (abfd, false))
 	    return -1;
@@ -1232,11 +1249,15 @@  elf_slurp_symbol_table (bfd *abfd, asymbol **symptrs, bool dynamic)
     }
 
   ebd = get_elf_backend_data (abfd);
-  symcount = hdr->sh_size / sizeof (Elf_External_Sym);
+  symcount = elf_tdata (abfd)->dt_symtab_count;
+  if (symcount == 0)
+    symcount = hdr->sh_size / sizeof (Elf_External_Sym);
   if (symcount == 0)
     sym = symbase = NULL;
   else
     {
+      size_t i;
+
       isymbuf = bfd_elf_get_elf_syms (abfd, hdr, symcount, 0,
 				      NULL, NULL, NULL);
       if (isymbuf == NULL)
@@ -1283,12 +1304,18 @@  elf_slurp_symbol_table (bfd *abfd, asymbol **symptrs, bool dynamic)
       if (xver != NULL)
 	++xver;
       isymend = isymbuf + symcount;
-      for (isym = isymbuf + 1, sym = symbase; isym < isymend; isym++, sym++)
+      for (isym = isymbuf + 1, sym = symbase, i = 1;
+	   isym < isymend;
+	   isym++, sym++, i++)
 	{
 	  memcpy (&sym->internal_elf_sym, isym, sizeof (Elf_Internal_Sym));
 
 	  sym->symbol.the_bfd = abfd;
-	  sym->symbol.name = bfd_elf_sym_name (abfd, hdr, isym, NULL);
+	  if (elf_use_dt_symtab_p (abfd))
+	    sym->symbol.name = (elf_tdata (abfd)->dt_strtab
+				+ isym->st_name);
+	  else
+	    sym->symbol.name = bfd_elf_sym_name (abfd, hdr, isym, NULL);
 	  sym->symbol.value = isym->st_value;
 
 	  if (isym->st_shndx == SHN_UNDEF)
@@ -1322,6 +1349,15 @@  elf_slurp_symbol_table (bfd *abfd, asymbol **symptrs, bool dynamic)
 		 moment) about the alignment.  */
 	      sym->symbol.value = isym->st_size;
 	    }
+	  else if (elf_use_dt_symtab_p (abfd))
+	    {
+	      asection *sec;
+	      sec = _bfd_elf_get_section_from_dynamic_symbol (abfd,
+							      isym);
+	      if (sec == NULL)
+		goto error_return;
+	      sym->symbol.section = sec;
+	    }
 	  else
 	    {
 	      sym->symbol.section
@@ -1402,7 +1438,10 @@  elf_slurp_symbol_table (bfd *abfd, asymbol **symptrs, bool dynamic)
 	  if (dynamic)
 	    sym->symbol.flags |= BSF_DYNAMIC;
 
-	  if (xver != NULL)
+	  if (elf_tdata (abfd)->dt_versym)
+	    sym->version = bfd_get_16 (abfd,
+				       elf_tdata (abfd)->dt_versym + 2 * i);
+	  else if (xver != NULL)
 	    {
 	      Elf_Internal_Versym iversym;
 
@@ -1440,13 +1479,15 @@  elf_slurp_symbol_table (bfd *abfd, asymbol **symptrs, bool dynamic)
     }
 
   free (xverbuf);
-  if (hdr->contents != (unsigned char *) isymbuf)
+  if (hdr->contents != (unsigned char *) isymbuf
+      && !elf_use_dt_symtab_p (abfd))
     free (isymbuf);
   return symcount;
 
  error_return:
   free (xverbuf);
-  if (hdr->contents != (unsigned char *) isymbuf)
+  if (hdr->contents != (unsigned char *) isymbuf
+      && !elf_use_dt_symtab_p (abfd))
     free (isymbuf);
   return -1;
 }
diff --git a/bfd/elflink.c b/bfd/elflink.c
index ce1407fa2dc..0e79d1f742d 100644
--- a/bfd/elflink.c
+++ b/bfd/elflink.c
@@ -3442,6 +3442,12 @@  elf_link_is_defined_archive_symbol (bfd * abfd, carsym * symdef)
   if (! bfd_check_format (abfd, bfd_object))
     return false;
 
+  if (elf_use_dt_symtab_p (abfd))
+    {
+      bfd_set_error (bfd_error_wrong_format);
+      return false;
+    }
+
   /* Select the appropriate symbol table.  If we don't know if the
      object file is an IR object, give linker LTO plugin a chance to
      get the correct symbol table.  */
@@ -4086,6 +4092,12 @@  elf_link_add_object_symbols (bfd *abfd, struct bfd_link_info *info)
   htab = elf_hash_table (info);
   bed = get_elf_backend_data (abfd);
 
+  if (elf_use_dt_symtab_p (abfd))
+    {
+      bfd_set_error (bfd_error_wrong_format);
+      return false;
+    }
+
   if ((abfd->flags & DYNAMIC) == 0)
     dynamic = false;
   else